1. Field of the Invention
The present invention relates to a luminous element which can be used for, for example, a display device. More particularly, this invention relates to a proposal of a new luminous element which uses a material capable of emitting light upon sensing pressure.
2. Description of Related Art
As various energies are applied to a substance, electrons in the substance transit from the ground state to the excited state and then return to the ground state, and the substance sometimes emits light. This is generally called a luminescence phenomenon. It has been confirmed that specific substances exhibit a tribo-luminescence phenomenon in which they emit light upon the application of friction or pressure.
For example, a treatise of R. Nowak et al. entitled xe2x80x9cEfficient Triboluminescence in N-isopropylcarbazolexe2x80x9d (Chemical Physics Letters, Vol. 94, No. 3, Jan. 21, 1983) describes that when pressure is applied to crystals of N-isopropylcarbazole, the crystals emit blue light of wavelengths of 400 nm to 500 nm. Moreover, a treatise of A. J. Smiel entitled xe2x80x9cTriboluminescence of Silica Core Optical Fibersxe2x80x9d (Appl. Phys. Lett. 40(2), Jan. 15, 1982) and a treatise entitled xe2x80x9cBroadband Triboluminescence in Silica Core Fiber Optic Waveguidesxe2x80x9d (Appl. Phys. Lett. 41(4), Aug. 15, 1982) describe that amorphous glass of SiO2 emits blue, red, or white light. Also, a treatise of Takada et al. entitled xe2x80x9cTransient Behavior of Mechanoluminescence from Europium Complex in Powder and in Polymer-Dispersed Filmxe2x80x9d (UPS-8, 1997) describes that a substance called Eu(TTA)3 emits red light. Furthermore, a treatise of J. I. Zink entitled xe2x80x9cAccounts of Chemical Researchxe2x80x9d (Vol. 11, No. 8, August 1978, p.p. 289-295) and a treatise of Linda M. Sweeting et al. entitled xe2x80x9cCrystal Structure and Triboluminescence 2. 9-Anthracenecarboxylic Acid and Its Estersxe2x80x9d (Chem. Mater. Vol. 9, No. 5, 1997, p.p. 1103-1115) describe a substance that exhibits a tribo-luminescence phenomenon.
Although research has been conducted on this tribo-luminescence phenomenon, the commercialization of such a phenomenon has not been realized.
By making use of the inventor""s experiences in a piezoelectric element, the commercialization of which has been promoted through years of studies, the inventor of this application has devised a specific structure to realize a luminous element and a display device, which utilize this tribo-luminescence phenomenon, and a method for manufacturing the luminous element and the display device.
It is an object of this invention to provide a piezoelectric luminous element which utilizes a tribo-luminescence phenomenon.
It is another object of this invention to provide a display device which utilizes the tribo-luminescence phenomenon.
It is still another object of this invention to provide a specific method for manufacturing a piezoelectric luminous element which utilizes the tribo-luminescence phenomenon.
It is a further object of this invention to provide a specific method for manufacturing a display device which utilizes the tribo-luminescence phenomenon.
This invention is a piezoelectric luminous element comprising:
a pressure luminous layer for emitting light upon the application of pressure; and
a piezoelectric element comprising a piezoelectric film held between electrode films and being located so as to be capable of applying pressure on the pressure luminous layer.
The pressure luminous layer is formed with any one luminescent material selected from a group consisting of N-isopropylcarbazole, silicon oxide glass, and Eu(TTA)3.
Moreover, the invention may be structured in a manner such that the pressure luminous layer and the piezoelectric element may be held between substrates such that the distance between these substrates will not change. It is desirable that of the substrates, the substrate placed in contact with the side of the pressure luminous layer where the piezoelectric element is not provided be capable of transmitting light.
This invention is a display device comprising the piezoelectric luminous element of the present invention, wherein the display device has a piezoelectric luminous unit, which is composed of at least the piezoelectric film, one of the electrodes, and the pressure luminous layer, and which is held between the substrates in a manner such that it can be activated independently in accordance with a picture element area.
Moreover, this display device may comprise a fluorescence conversion layer for converting the wavelength of the pressure luminous layer in accordance with the piezoelectric luminous unit on the substrate placed in contact with the light-emitting side of the pressure luminous layer.
Furthermore, the display device may comprise a color filter for transmitting a specific wavelength in accordance with the piezoelectric luminous unit on the substrate placed in contact with the light-emitting side of the pressure luminous layer.
This invention is a method for manufacturing a piezoelectric luminous element, comprising the steps of:
forming a lower electrode over a substrate;
forming a piezoelectric film over the lower electrode;
forming an upper electrode over the piezoelectric film;
forming a pressure luminous layer for emitting light upon the application of pressure on the upper electrode; and
attaching a substrate to the pressure luminous layer.
For example, the step of forming the pressure luminous layer comprises the steps of:
applying a mixture of a resin and N-isopropylcarbazole powder to the upper electrode; and
drying the applied mixed resin at a constant temperature.
Also, for example, the step of forming the pressure luminous layer comprises the steps of:
forming an amorphous silicon film over the upper electrode; and
forming a silicon oxide glass film by giving thermal treatment to the silicon film in an oxygen atmosphere.
Moreover, the step of forming the pressure luminous layer comprises the steps of:
generating a methylene chloride solution by mixing polycarbonate and a europium compound;
applying the solution to the upper electrode; and
drying the applied solution.
Furthermore, the step of forming the piezoelectric film comprises the steps of:
applying, drying and pyrolyzing a piezoelectric ceramic precursor; and
crystallizing the piezoelectric ceramic precursor.
In the step of crystallizing the piezoelectric ceramic precursor, crystallization is caused by laser irradiation, dipping in an alkali solution of fixed concentration, or high temperature thermal treatment.
This invention is a method for manufacturing a display device, comprising the steps of:
forming a lower electrode over a substrate;
forming a piezoelectric film over the lower electrode;
forming an upper electrode over the piezoelectric film;
forming a pressure luminous layer for emitting light upon the application of pressure on the upper electrode;
etching the piezoelectric film, the upper electrode, and the pressure luminous layer in a pattern corresponding to a picture element area; and
attaching a substrate to the etched pressure luminous layer.